During the past year we have investigated the prevalence and clinical correlates of attention deficit hyperactivity disorder (ADHD) under the definitions of DSM-IV and DSM-5 using NHANES/CDISC data. The results showed that extension of the age-of-onset criterion from 7 to 12 years lead to about a 30% increase in the prevalence of ADHD. The clinical significance of the early and later age of onset groups is comparable supporting the DSM-5 extension of the age of onset criterion in ADHD. Public Health Impact: These findings report the implications of extending the age of onset of ADHD symptoms from 7 to 12 years of age, as stipulated by the DSM-5, using parent reports from the nationally representative sample of adolescents. The study is essential to integrate data about the developmental nature of the disorder into diagnostic criteria that are valid and useful. Future Plans: Several ongoing projects using the NHANES and CDISC data include: 1) examining the association between threshold and subthreshold major depressive disorder and inflammatory and vascular biomarkers (Marques et al, 2014 ready for submission); and 2) evaluating the relationships between self-reported physical activity or objectively measured physical activity and mental disorders.